std. 10.4 in sexually reproducing organisms, each offspring contains a mix of characteristics...

Std. 10.4 In sexually reproducing organisms, each offspring contains a mix of characteristics inherited from both parents.

D 37. Use the Punnett square technique to predict the distribution of traits in mono- and di-hybrid crossings.

Learning Target: Principles of Heredity

I Can…Explain the foundation principles of Mendelian Genetics

I Will…• Briefly describe Mendel’s contribution• Describe Mendel’s experimental design• Describe Mendel’s conclusions and Law of

Segregation• Define basic hereditary terms• Distinguish between genotype and phenotype

All started with Austrian monk Gregor Mendel in the 1800s.

Mendel showed that:• Traits are inherited as discrete units.• Laid groundwork of genetics• Demonstrated patterns of

inheritance

Mendel used purebred, self-pollinating pea plants with a selection of • “either / or” traits including:• Pea shape, pea color, pod shape, pod color,

plant height, flower color, and flower position.

Mendel’s Experimental Design:• Use of self-pollinating pea plants• Can control reproduction of plants• Reproduce quickly• Self-pollination creates genetically “pure”

genetic lines• “Either / Or” Traits• Only two allele versions for each trait studied• No blending of traits• Dominant v. Recessive

• Good scientific method (controlled variables and one I.V.)

• Many trials / reproduced results (validity)_

Mendel’s Experimental Design:

Cross – mating of two organisms• P1 – Parental generation

• F1 – First Filial (first offspring) generation

• F2 – Generation produced from F1

Law of Segregation:• Organisms donate only one copy of

each gene in the gametes (haploid) to their offspring

• Genes segregate or separate during meiosis• Remember the process of meiosis

segregates only one of each chromosome into each of the gametes

Mendel’s Conclusions

Vocabulary terms:• Genetics – study of biological

inheritance patterns and variation in organisms

• Trait – distinguishing characteristic that is inherited e.g. earlobe attachment, freckles, hairline pattern

• Gene – section of DNA that codes for a protein e.g. hemoglobin for RBCs

• Allele – different versions of a gene e.g. normal or sickle hemoglobin

Genetics and HeredityCh. 6.3 pp. 177-179Ch. 6.4 pp. 180-182

Vocabulary terms:• Homozygous – two of the same allele at

the same gene locus (location on chromosome) for a trait e.g.

Gene trait = earlobe attachment

• A homozygous individual would have: • 2 unattached earlobe alleles or • 2 attached earlobe alleles

• Purebred – genetically uniform

Genetics and Heredity

Vocabulary terms:• Heterozygous – two different alleles at

the same gene locus (location on chromosome) for a trait e.g.

Gene trait = earlobe attachment


• A heterozygous individual would have: • 1 unattached earlobe allele and • 1 attached earlobe allele

• Hybrid - NOT genetically uniform

Vocabulary terms:• Dominant - allele that is expressed

even when 2 different alleles are present e.g. unattached allele is dominant to attached allele in earlobe attachment


Heterozygous E e

Homozygous E E Designated with an uppercase (capital) letter representing the trait e.g. “E” = Dominant earlobe attachment (unattached)

Vocabulary terms:• Recessive - allele that is expressed

only when 2 of the same allele are present e.g. attached allele is recessive and will only show if 2 attached alleles are present for earlobes


Homozygous attached e e

Designated with a lowercase (small) letter representing the trait e.g. “e” = recessive earlobe attachment (attached)

Vocabulary terms:• Genotype – Genetic makeup of an

organism; actual genes present • Homozygous unattached earlobes (E E)• Heterozygous unattached earlobes (E e)• Homozygous attached earlobes (e e)


Vocabulary terms:• Phenotype – physical appearance of

trait in organism from expression of allele• Unattached earlobes • Could be (EE) or (Ee) genotype• Phenotype shows • Dominate version

• Attached earlobes• Must be (ee) genotype• Phenotype of recessive only shows • When homozygous recessive

genotype


• Phenotype – Dominant trait• Genotype – Could be either:• Homozygous Dominant – e.g. EE• Heterozygous – e.g Ee


• If you know the genotype you will know the phenotype, BUT…

• If you know the phenotype you cannot know the genotype of a dominant trait without more information

• Phenotype – Reccessive trait• Genotype – Must be :• Homozygous reccessive – e.g. ee

Vocabulary terms:• Genome – all of

an organism’s genetic material• Human somatic

cells have 46 chromosomes in 23 pairs

• Estimated to contain 25,000 genes


Learning Check √: Principles of Heredity

Considering Ms. Brown has unattached earlobes and her son has attached earlobes and her daughter has unattached earlobes, • What is Ms. Brown’s genotype? ________________• What is Ms. Brown’s son’s genotype? ______________• How did you figure this out?

• Can you determine Ms. Brown’s daughter’s genotype? Explain Why or Why not.

std. 10.4 in sexually reproducing organisms, each offspring contains a mix of characteristics...

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